Curvilinear design is an underutilized construction strategy which is known to enclose space with ten to twenty percent less material than conventional rectangular structures, provide structural stability with less material, resist the impact of wind and water more efficiently than rectangular structures, and offer significant energy savings in operating cost. Unlike many initiatives in building today that are promoted as energy-saving and cost-effective, such as solar collector panels or high tech insulation, curvilinear design addresses the fundamental factor—the shape of the structure—which drives up material and energy costs. The conventional rectangular building is inherently less energy efficient and more costly to build and operate.
The benefits of curvilinear design in structures for living and for enterprise have long been recognized, from the yurt housing of nomadic tribes to round barns in America first constructed in the 18th century. In 1910, the benefits of these cylindrical barns in America were documented in a Kansas State Board of Agriculture study, which noted that, “the rectangular form requires 22 percent more wall and foundation to enclose the same space; and that the cost of material is from 34 to 58 percent more for the rectangular building.”
Round barns date back to late 18th century. The benefits of these curvilinear barns were well understood by progressive farmers and were the dominate shapes used to build new barns in the United States during the late 19th century. The benefits realized by building curvilinear barns included savings in materials, erection time, structural stability, and energy, as well as improved functionality. These benefits were well documented in a study from the Kansas State Board of Agriculture, Eighteenth Biennial Report, 1911-1912, pps. 139-142 on the efficiency of round barns where a farmer can “save from 30% to 40% of the cost of a rectangular barn by constructing a round barn of quite similar area.” These structures utilizing the benefits of cylindrical walls and conical roofs were made primarily out of straight pieces of wood.
Curvilinear design for production scale has faced unresolved hurdles and remained an untapped opportunity. In the 1970s, Mr. Jason Purdy pioneered a construction method that combined air pressure and highly efficient insulation materials to form curvilinear building shapes. In these projects, an insulating/structural plasticized foam was sprayed onto an existing inflatable form or “balloon” to form the structure. The largest structure built by Mr. Purdy was a storage building five stories high and 110 feet in diameter, with no interior columns, for Holly Sugar Corporation. Other structures built by the Mr. Purdy included an aircraft hanger, offices and homes. This method of constructing curvilinear buildings is still utilized in the industry today. While overcoming some of the problems of inflexible, complex systems, this approach still requires skilled onsite labor, high transportation costs and expenses related to the need for a framework.
In describing the background of the invention, it is beneficial to briefly discuss certain prior art patents and their shortcomings. A first patent, U.S. Pat. No. 4,155,967, provides a method of lining a passageway with a hard, rigid pipe of thermosetting resin, wherein a tubular fibrous felt is immersed in the resin to form a carrier for the resin. The immersed felt and resin have an inflatable tube therein and this tube is inflated to shape the resin to the passageway surface. The resin is cured to form the hard, rigid lining pipe with the felt embedded therein. This invention starts with a flexible material with a felt lining impregnated with un-catalyzed plastic foam material, that can be installed (as a flexible liner) into an existing underground pipe and then catalyzed into a strong, smooth, hard pipe liner to repair existing broken or leaking pipes. The purpose of this invention is to rehabilitate existing underground pipes and avoid the disruption and expense of having to excavate the length of an underground pipe system for repairs. This serves only as an interior liner for underground pipes and is not used or intended as an independent, free standing, structural system.
A second patent, U.S. Pat. No. 3,277,219, provides a curvilinear building using an inflated form and on-site spraying of a plasticized foam material. This building system enjoyed the benefits of pre-manufactured inflatable forms that were light in weight and a lightweight plasticized foam material mixed/catalyzed and sprayed on-site onto the inflated form to produce a monolithic shell. The disadvantage of this system was that the foam materials had to be applied to the inflated form by specially skilled technicians, using highly specialized mixing and spraying equipment, and other specialized equipment (such as expensive and potentially dangerous temporary scaffolding equipment inside larger structures). This construction process was also vulnerable, during the extended period of time required by the on-site labor, to the uncertainties of weather (wind, rain, temperature fluctuations) before the building could be hardened into a free standing structure.
Another system to construct basically curvilinear structures using inflatable forms and on-site spraying of plasticized foam onto an inflated membrane is disclosed in U.S. Pat. No. 3,277,219. This patent teaches a building formed by an inflatable form and insulation layers of urethane foam are applied to the undersurface of the form. Hanger members are secured to the foam layer by adhesively affixing planar base portions of the hangers to the foam layer where after additional foam is applied to embed the hanger bases. Reinforcing mesh is secured to and supported by the hangers followed by the application of one or more layers of a cementitious material, which is allowed to cure. Air pressure beneath the form is progressively increased to maintain a substantially constant uplift force on the foam. The inflatable form may be removed after curing and a protective coating applied to the outer exposed surface of urethane foam to protect it from ultraviolet degradation. This invention shares the same disadvantages of on-site application of plasticized foam, as delineated above in the process of U.S. Pat. No. 3,277,219.
A third patent, U.S. Pat. No. 3,197,927, provides a tubular and structural frame and panel building system used to construct curvilinear structures from pre-manufactured parts and referred to as the geodesic dome. Unfortunately, this invention requires expensive tooling to manufacture the original parts, requiring bulky transportation of the rigid and heavy components, requiring time consuming and specialized on site labor and equipment to assemble the house, and requiring expensive retooling to manufacture each change in dimension. Another disadvantage of this building system was that it was made of multiple rigid parts that had to be sealed on site, where the assembled parts had joints that often faced the sky and remained vulnerable to leaking from rain and snow or expansion and contraction caused by changes in temperature.
It is also known that factory built modular homes/buildings provide a process of building a finished home by dividing a building into rectangular modules that are approximately 12′×12′ and up to 60′ long (a size contingent on legal trucking limits of roads and bridges), then at the site, lifting the modules onto a foundation with a crane and combining the modules on-site into a completed building. The advantage of this system is that approximately 80% of the construction occurs indoors, on a more efficient assembly line for parts and labor and the assembly time of a structure is reduced to 10% of the time required to build a stick-built house. The disadvantage is that the sizes and proportions are limited to the dimensions required by transporting the modules down a highway, dimensions that are unrelated to the qualities or functions of a building. Also, the modules of this building system suffer from an extremely wasteful and inefficient package for transportation in which over ninety percent of the package (module) being trucked to a site is not product, but air or empty space. Another variant of this building system is mobile homes, a building segment comprising over fifteen percent of new homes built in the U.S. This is a building system where the trailer and wheels transporting the building from the factory to the site is left in place to serve as the foundation of the building to take the place of a more permanent concrete foundation. Mobile homes suffer the same disadvantages as listed above for factory built modular homes/buildings. It is noted that manufactured homes made up twelve percent of the new home construction in the United States in 2008.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.